Digital audio broadcasting systems (DAB) envisage, according to the international standards ETS 300.401, four different broadcasting modes, each of which is characterized by different combination of values assigned to time/frequency parameters relative to the COFDM modulation (Coded Orthogonal Frequency Division Multiplexing). Of course, the broadcast medium may be different (cable, terrestrial free space, satellite, or optical fiber), though the medium more widely used for this type of broadcasting is optical fiber. The broadcasting mode is not strictly tied to the broadcast medium even if this parameter is important for choosing the mode.
Generally speaking, for a given broadcasting medium and for certain frequency bands, one broadcasting mode might be more adequate than another.
One of the key components of DAB receivers being developed is an ASIC device that integrates the necessary circuit for the COFDM mode modulation. Among other fundamental functions, this integrated device calculates the Fast Fourier Transform (FFT), the Inverse Fast Fourier Transform (IFFT), and performs a differential demodulation of the received signal.
A first generation of these ASIC devices has already been produced and developed, however these devices cannot support an automatic detection of the broadcasting mode of the signal received. Furthermore, such a fundamental input relative to the broadcasting mode must be manually supplied to the device via hardware selection.
Therefore, there exists a clear need and usefulness for an automatic broadcasting mode detection system that may be easily integrated into the ASIC device of COFDM mode modulation, so to eliminate the need to provide, from external sources, an indication of the broadcasting mode, in order to correctly set the COFDM mode modulation parameters.